Introduction to Quantum Computing

 

Why quantum: How big is a bit?

 

In this lesson, you will predict the size of a single piece of information storage.

 

1)      What is a bit?

Have a look at the Wikipedia page: https://en.wikipedia.org/wiki/Bit

A bit is a binary digit, and can be in only one of two states at a time: the two states are most commonly represented as either a 0 or 1. It stores the smallest possible piece of information in a computer.

The international symbol for ‘power’ includes the number ‘1’ (one) and ‘0’ (zero) within it.

 

2)      How do you build a bit?

Well, you could construct a computer in Minecraft. See YouTube videos: https://www.youtube.com/playlist?list=PLDN4M7O4MGcNtzYQO1oBFKYbY59jR59f9

https://www.youtube.com/watch?v=fYIBlJmNwTE [16 bit computer by Sw1Ftx16]

In the real world, here are some ways in which manufacturers build storage elements for computers:

This one shows how to use an existing electronic chip (integrated circuit) - http://www.instructables.com/id/Make-a-one-chip-RAM-random-access-memory/

The integrated circuits that make computer storage chips are known as RAM (random access memory). Here is a factory tour: https://www.youtube.com/watch?v=EWDirCg-Wu8

To understand how a RAM chip works, please see: https://computer.howstuffworks.com/ram.htm

You might see that bits are usually stored in groups of 8. A group of 8 bits is usually called a byte.

 

3)      Webquest to predict bit sizes in the future

Bits come in different sizes. Let’s look at how big a bit can be, by looking at computer storage devise in the past and future. Look at these websites to complete the table.

HINT: to work out the size of one bit, find the volume of each storage device, and divide by the number of bits it can store.

Year

Commercially available storage device

Length (mm)

Width (mm)

Height(mm)

Volume (mm3)

Storage capacity (bits) (multiply by 8 if stated as bytes or characters)

Volume of each bit (mm3)

1946

Selectron Tube

254

76

76

1467104

1024

1433

1951

Mercury delay line

 

 

 

 

1600 x 8 = ??

 

1952

Magnetic Core

 

 

 

 

 

 

1956

Hard Disk

 

 

 

 

5,000,000 x 8

 

1970

Dynamic RAM solid state integrated circuit Intel 1103

7

3

.1

 

 

 

1984

Compact-Disc CD-ROM

 

 

 

 

 

 

2000

Secure Digital flash memory card

 

 

 

 

64MB

64,000,000 x 8

 

2018

micro-SD card

 

 

 

 

 

 

???? (you predict)

single-atom memory

-

-

-

9.97x10-21

1

1 atom = 9.97x10-21

If you put this into a spreadsheet, remember that big and small numbers are expressed in ‘exponential notation’. So, 5x103 (5,000) is written as 5E3 in Excel. Format cells as ‘scientific’ to see this notation. You may find it easier to see the graph if you take the logarithm of the bit-volumes. In that case, the log of the volume of one atom would be -20, so can you predict in what year bit sizes might get there?

 

4)      Conclusion and check quiz

When you have plotted the size of a bit against the invention year, you should be able to predict when a bit will be as small as an atom (9.97x10-21 mm3).

Others have done similar predictions. You can find many of them on the internet, perhaps at Singularity.

When a ‘bit’ gets as small as a single atom, we are talking about quantum computing.

 

Figure 1: Single Atom in Ion Trap

 

Homework

Find out if your prediction conforms with Moore’s Law.

Figure 2: A closer look.

When illuminated by a laser of the right blue-violet colour, the atom absorbs and re-emits light particles sufficiently quickly for an ordinary camera to capture it in a long exposure photograph.

The first ever photograph of light as both a particle and wave

Figure 3: The first ever photograph of light as both a particle and wave

 There is a quiz on the contents of this lesson. Click the button below to take the quiz.

Check quiz: How big is a bit?

 

 

 

 

 

Credits:

Figure 1: Single Atom in Ion Trap (David Nadlinger/University of Oxford/EPSRC) https://qz.com/1205279

Figure 2: A closer look. (David Nadlinger/University of Oxford/EPSRC)

Figure 3: The first ever photograph of light as both a particle and wave. https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2015/1-thefirstever.jpg